The present invention relates generally to the art of bearings for facilitating shaft rotation. More particularly, the invention relates to a bearing apparatus having an integrated load sensing arrangement.
In many applications, the load present on a rotating shaft can vary during use. For example, shafts utilized in industrial stirring operations will often accrue material as the shaft turns. At some point, the load on the shaft can exceed a desirable threshold, leading to shaft breakage or other maintenance considerations.
Devices have been developed in the past to monitor shaft load. These devices have generally included specialized load cells placed under the housing of a bearing apparatus utilized to rotatably support the shaft. Alternative designs have also been employed to simplify the arrangement, but these alternative designs have often been bulky, cumbersome and costly.
The present invention recognizes and addresses the foregoing disadvantages, and others, of prior art constructions and methods. Accordingly, it is an object of the present invention to provide a novel bearing apparatus.
It is a further object of the present invention to provide a bearing apparatus having an improved load sensing arrangement.
It is a particular object of the present invention to provide a bearing apparatus having a load sensing arrangement incorporated into the bearing housing.
It is a particular object of the present invention to provide a bearing apparatus including one or more load sensors operative to determine shaft load based on housing deformation.
It is also an object of the present invention to provide improved methodology for determining shaft load.
Some of these objects are achieved by a bearing apparatus for supporting a rotatable shaft. The bearing apparatus comprises a bearing housing having a bearing set disposed therein. The bearing set includes first and second opposed elements capable of relative rotation. One of the first and second opposed elements is fixed with respect to the shaft for rotation therewith.
The bearing apparatus further includes at least one load sensor located within the bearing housing for providing an electrical indication of loading on the rotatable shaft. Preferably, each such load sensor is fixed with respect to the bearing housing. For example, each load sensor may comprise a strain gauge, such as a rosette strain gauge, having electrical characteristics that vary as the bearing housing is deformed.
In some exemplary embodiments, a pair of load sensors may be utilized, radially separated from the shaft. In this case, the pair of load sensors are also preferably spaced apart from each other by a predetermined angular separation.
Typically, the bearing set may comprise a bearing insert in which the first and second opposed elements comprise respective inner and outer rings thereof. A plurality of bearing elements are disposed in the region between the inner and outer rings. In such embodiments, the bearing housing may define a recess, radially external of the outer ring, in which the load sensors are located. For example, a pair of angularly separated load sensors may be located in the recess.
The bearing apparatus may further comprise power and detection circuitry in electrical communication with the load sensor. Often, the detection circuitry will be configured to provide a voltage signal indicative of loading on the shaft. Current output circuitry may be utilized to provide a current output signal based on the voltage signal. It will often be desirable to mount the various circuitry to an exterior of the bearing housing.
Other objects of the present invention are achieved by a bearing apparatus for supporting a rotatable shaft having a bearing housing and a bearing set disposed therein. A plurality of load sensors are also located within the bearing housing for providing an electrical indication of loading on the rotatable shaft. Preferably, the load sensors are radially separated from the shaft and are spaced apart from each other by a predetermined angular separation. The bearing housing may define an arcuate recess radially spaced from the shaft, in which the load sensors are fixed.
Still further objects of the present invention are accomplished by a bearing housing comprising a housing structure defining a shaft opening about a central axis. The housing structure also defines an interior cavity configured to receive a bearing insert. In addition, a recess having at least one strain gauge fixedly located therein is defined at a predetermined location on a surface of the housing structure, such as an interior surface thereof. The strain gauge exhibits electrical characteristics that vary as the housing structure is deformed.
In some exemplary embodiments, the recess is configured as an arcuate recess radially spaced from the central axis. For example, where the housing structure comprises top and bottom matable portions, the arcuate recess may be defined in the bottom matable portion. In such embodiments, a plurality of strain gauges may be located in the recess, separated from each other by a predetermined angular separation.
The housing may also include power and detection circuitry mounted to an exterior thereof. Electrical communication between the external circuitry and the strain gauges may be provided by electrical wires extending through a bore defined in the housing structure.
Additional objects of the present invention are achieved by a method for detecting loading on a rotating machine element. One step of the method involves supporting the machine element in rotation utilizing a bearing apparatus including a housing and at least one bearing set disposed therein. As a further step, deformation of the housing due to loading on the machine element is detected. Preferably, housing deformation may be detected utilizing a strain gauge fixed to the bearing housing. A deformation signal representative of housing deformation is then generated.
According to exemplary methodology, the deformation signal may be further conditioned to provide an indication of loading on the rotating machine element. For example, where the deformation signal is a voltage signal, a current output signal may be produced based on the voltage signal.
Other objects and aspects of the present invention are provided by various combinations and subcombinations of the disclosed elements, which are discussed in greater detail below.